Fluid-pressure motor



March 17, 1931. NELL 1,796,389

FLUID PRESSURE MOTOR Filed Oct. 25, 1928 INVENTOR. Gusfave M A/e// A TTORNEY.

Patented Mar. 17, 1 931 UNITED STATES PATENT OFFICE GUSTAVE M. N ELL, OF DETROIT, MICHIGAN ASSIGNOR TO CHICAGO PNEUMATIC TOOL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY rtnrn-rnnssunn vro'ron Application filed October 25, 1928. Serial No. 314,893.

This invention relates to fluid pressure I motors with special relation to those of the percussive type in which the reciprocations of the percussive member are controlled by a pressure fluid distributing valve which is moved automatically in timed relation with the movements of the piston.

7 One object of the invention is to devise control mechanism for a fluid pressure-motor which is positive in action and of sturdy con struction. Another object is to use a simple compact valve and to keep the main ports between the piston and valve chambers short. Other objects will be apparent from the detailed description which follows.

In order to illustrate the invention, a pre- 'ferred form thereof is shown in the accompanying drawings in which Figs. 1 and 2 are longitudinal sectional views showing the positions of the moving parts at the beginning and at the end respectively of the piston stroke.

The embodiment of the invention chosen for the purpose of illustration comprises a 5 pneumatic percussive tool having a cylinder 3 providing a piston chamber within which reciprocates an impact member or piston 4 arranged'to impart blows to a working tool, such as a'drill steel 5 supported in a front head 6. While the piston may strike the drill steel directly, if desired, in the present instance the blow is imparted through an anvil block 7 interposed between steel 5' and piston 4:, the block being slidably mounted in a guide member 8 between cylinder 3 and front head 6. The cylinder is provided with an exhaust chamber provided by an inner transverse annular groove 9 substantially centrally of the piston chamber and communicating directly with atmosphere throughone or more ports 10. This exhaust chamber is controlled by piston 4 and is arranged to beoverrun' by the latter in both directions. The rear end of the piston cham- 45 her is closed by a plug member 11 secured in place by back head 12. To reduce the weight of piston 1, the same may be provided with a 'rearwardly opening cavity or recess 4a and the capacity. ofthe rear end of the piston by forming plug 11 with an extension 1111,

which is received by socket 4a of the piston.

Cylinder 3 also provides a valve chamber in which is disposed an automatically thrown valve 13 arranged to move in timed relation with piston 4 and to control the distribution of motive fluid from inlet 14 to the opposite ends of the piston chamber to drive the piston alternately in both directions. Valve 13 is of substantial length and is disposed in parallelism with the piston chamber and closely adjacent thereto so that the connecting ports and passages are relatively short and direct. Motive fluid for driving the piston on its working stroke (Fig. 1) enters the piston chamber by a port 15a from chamber 15 under control of the rear end of the valve 7 and motive fluid for the return stroke (Fig.

2) passes axially through the bore of valve 13, thence transversely into valve chamber 16, axially through passages 17, to chamber 18 and thence through a passage 18a directly into the piston chamber. The ends of valve 13 are dlfferentlal 111 size thereby providing differential pressure areas, the smaller area tinuously vented to atmosphere, the real ward face by a large vent 24- and the forward face 23 by a restricted vent 25. A passage 26 extends from valve area 23 to the piston chamber under control of piston 1 for ad mitting pressure fluid to shift the valve rearwardly. By reason of restricted vent 25, passage 26 also acts as an auxiliary exhaust for the rear end of the piston chamber on the rearward stroke of thepiston (Fig. 2). On the forward stroke of the piston (Fig. 1)

- there is likewise an auxiliary exhaust for the chamber. is keptdown .to .therequired. amount front end-of the piston, this exhaust utilizing main exhaust chamber 9 and being under control of valve 13, the air head of the piston passing out through inlet passage 18a, chamber 18, axial passages 17, valve chamber 16, around and along an exterior groove 27 in the valve to valve chamber 28 and thence by a passage 29 to exhaust chamber 9.

The operation of the motor is as follows. \Vith the parts in the position shown in Fig. l, motive fluid enters by inlet 14;, valve chamber 15, inlet port 15a driving piston 4 forwardly. Pressure obtains against areas 19, 29, and 21, of the valve but since the sum of areas 19 and is greater than area 20, the valve is held in the position shown. As the piston advances, it covers main exhaust chamber 9 but the air ahead of it continues to escape through the auxiliary exhaust comprising passage 18a, chan'iber 18, passages 17, chamber 16, valve groove 27, chamber 28, passage 29, and exhaust chamber 9. hen the piston uncovers passage 26 (Fig. 2) mo tive fluid from the rear end of the piston chamber builds up against shift area 23 of the valve since passage 26 is much larger than the restricted vent 25. The sum of the pres sures on areas 23 and 20 thereupon overcome the pressures obtaining on valve areas 19 and 21 and the valve is shifted rearwardly at least to the extent of cutting off the admission of motive fluid to the rear end of the piston chamber through port 15a before the rear end of the piston uncovers exhaust chamber 9. Vhen exhaust chamber 9 is uncovered by piston 4 the pressure upon valve areas 21 and 25 is immediately relieved but since valve area 20 exceeds valve area 19, the valve completes its rearward movement and is held in its rearward position with the motive fluid flowing through passages 17, chamber 18, and chamber 18a. to the front end of the piston to be ell'ective to drive the piston rearwardly immediately after the latter has struck anvil block 7. As the piston moves rearv'ardly it closes exhaust chamber 9, but the air rearwardly of it continues to escape tl'irough passage 26 and restricted vent port 25 until passage 26 is covered. Thereupon the air which is trapped by the piston is compressed by the latter and builds up pressure against valve area 21. As soon as the pressure on areas 19 and 21 exceed the pressure on the lesser valve area 20, the valve moves forwardly thus cutting off the supply of motive fluid to the front of the piston chamber and this occurs before the piston uncovers main exhaust chamber 9. The momentum of the piston carries it rearwardly against the motive fluid now admitted by the valve through port 15a (Fig. 1) until it uncovers main exhaust chamber 9 thus venting the forward piston chamber in preparation for the forward stroke of the piston. The valve continues in its forward position since. the sum of the areas 19 and 21 exceeds the area 20. This completes the cycle of operation.

To speed up the building up of pressure against valve area 21 to effect forward movement of the valve, a small radial port 30 may be provided in valve 13 to pass a limited amount of live motive fluid at all times into valve chamber 15 but this is ordinarily not necessary.

From the above it will be apparent that an important feature of the present invention is the shifting of the valve in both directions prior to the uncovering of the main exhaust chamber 9 by the piston. This prevents waste of motive fluid since none of it can pass directly from the inlet to exhaust through the piston chamber. The Valve control arrangement herein disclosed not only provides for accurate timing so that the full force of the pressure fluid is available to strike a heavy blow but the motor is exceptionally economical in the use of motive fluid, since none is lost without performing Work.

\Vhile the invention has been herein disclosed in what is now considered to be a preferred form, it is to be understood that the invention is not limited to the specific details thereof, but covers all changes, modifications, and adaptations within the scope of the ap pended claims.

I claim as my invention:

1. In a fluid pressure percussive motor in combination, a cylinder providing a piston chamber, a piston reciproeable therein, and an automatically thrown valve for controL ling the distribution of motive fluid for ac tnating said piston, said valve being tubular and arranged to receive the motive fiui d thereWithin and to control its access to said piston chamber by the ends thereof, said ends of said, valve presenting differential end areas, said. valve having an additional pressure area adjacent the smaller of said differential areas and always in connnunication with one end of the piston chamber so as to be subject to. air compressed by the piston at one end of its stroke thereby to assist the pressure of the live motive fluid upon the smaller of said differential end areas to over come the pressure on the opposed larger di'tl.

fercntial area thereby to shift the valve.

2. In a fluid pressure percussive motor in combination, a cylinder providing a piston chamber, a piston reciprocable therein and an automatically thrown valve for control ling the distribution of motive fluid for actuating said piston, said valve being tubular and arranged to receive the motive fluid therewithin and to control its access to said piston chamber by the ends thereof, said ends of said valve presenting differential end areas, said valve havingan annular enlargement forming a shoulder providing an additional pressure area adjacent the smaller of said differential,

' areasv and always. in communication with the.

rear end of said piston chamber so as to be subject to air compressed by said piston on its rearward stroke thereby to assist the pressure of the live motive fluid upon the smaller of said differential end areas to overcome the pressure on the opposed larger differential area, thereby to shift the valve.

3. In a fluid pressure percussive motor in combination, a cylinder providing a piston chamber, a piston reciprocable therein, and an automatically thrown valve for controlling the distribution of motive fluid for actuating said piston, said valve being tubular and arranged to receive the motive fluid therewithin and to control its access to said piston chamber by the ends thereof, said ends of said valve presenting differential end areas, said valve having an additional pressure area adjacent the smaller of said differential areas and always in communication with one end of the piston chamber so as to be subject to air compressed by the piston at one end of its stroke, said valve having a fourth pressure area of greater extent than said additional area and the smaller of said diflerential area when combined and for overcoming the latter, and means under control of said piston for admitting motive fluid from said piston chamber to said fourth area of said valve.

4. In a fluid pressure percussive motor, in combination, a cylinder providing a piston chamber, a piston reciprocable therein, and an automatically thrown valve for controlling the distribution of motive fluid for actuating said piston, said valve being tubular and arranged to receive the motive fluid therewithin and to control its access to said piston chamher by the ends thereof, said ends of said valve presenting differential end areas, said valve having an annular enlargen'ient forming a shoulder providing an additional pressure area adj acent the smaller of said diflerential areas, and always in communication with the rear end of said piston chamber so as to be subject to air compressed by said piston on its rearward stroke, thereby to assist the pressure ofthe live motive fluid upon the smaller of said'differential end areas to overcome the pressure on the opposed'larger diflerential area thereby to shift the valve, said valve having a fourth area opposed to the smaller of saidrdiiferential areas and to said additional area and greater than both the latter, and a passage in said cylinder arranged to be uncovered by said piston on its forward or'working stroke to admit pressure fluid to said fourth area to shift said valve.

5. In a fluid pressure percussive motor, in combination, a cylinder providing a piston chamber, a piston reciprocable therein, and an auton'latically thrown valve 'for controlling the distribution of motive fluid for actuating said piston,saidvalve being tubular and arranged to receive the motive fluid therewithin and to control its access to said piston chamber by the ends thereof, said ends of said valve presenting differential end areas, said valve having an annular enlargement forming a shoulder providing an additional pressure area adjacent'the smaller of said differential areas, and always in communication with the rear end of said piston chamber'so as to be subject to air compressed by said piston on differential areas and to said additional area and greater than both the latter, and a passage in said cylinder arranged to be uncovered by said piston on its forward or working stroke to admit pressure fluid to said fourth area to shift said valve, said cylinder providing a continuously open vent of restricted size for said fourth area.

6. In a fluid pressure percussive motor, in combination, a cylinder providing a piston chamber, a piston reciprocable therein, and an automatically thrown valve for controlling the distribution of motive fluid for actuating said piston, said valve being tubular and arranged to receive the motive fluid therewithin and to control its accessto said piston chamber by thereby to assist the pressure of the live motive fluid upon the smaller of said differential end areas to overcome the pressure on the opposed larger difl'erential area, thereby to shift the valve, said'valve having a flange providing a fourth area opposed to the smallerof said differential areas and to said additional area and greater than both the latter in combination, a passage controlled by said piston for admitting pressure fluid from said piston chamber to said fourth area on the forward stroke of said piston to effect shifting of said valve, said cylinder providing continuously open vents for both sides of said valve flange,

the vent for said fourth area being small in 'stantially centrallyof said piston chamber under control of said piston and having a vent s to atmosphere, an automatically thrown distributing valve moving in timed relation with said piston for controlling the movements of the latter, and means utilizing said exhaust smaller of said i ehamber to provide an exhaust for one end of said piston chamber while said exhaust chamber is covered by said piston.

8. A fluid pressure percussive motor comprising a cylinder providing a piston chamber, a piston reciprocable therein, said cylinder providing an exhaust chamber substantially centrally of said piston chamber under control of said piston, and having a vent to atmosphere, an automatically thrown (listributing valve moving in timed relation with said piston for controlling the movements of the latter, and means under control of said valve and utilizingsaid exhaust chamber while covered by said piston to provide an exhaust for the forward part of said piston chamber on the forward stroke of said piston.

9. A fluid pressure percussive motor comprising a cylinder providing a piston chamber, a piston reciprocable therein, said cylinder providing an exhaust chamber substantially centrally of said piston chamber under control of said piston and having a vent to atmosphere, an automatically thrown distributing valve moving in timed relation with said piston for controlling the movements of the latter, and means under control of said valve and utilizing said exhaust chamber while covered by said piston to provide an exhaust for the forward part of said piston chamber on the forward stroke of said piston including a recess in the exterior of said valve.

10. In a fluid pressure percussive motor in combination, a cylinder providing a piston chamber, a piston reciprocable therein, and an automatically thrown valve for controlling the distribution of motive fluid for actuating said piston, said valve being tubular and arranged to receive the motive fluid therewithin and to control its access to said piston chamber by the ends thereof, said ends of said valve presenting differential end areas, said valve having an additional pressure area adjacent the smaller of said differential areas and always in communication with one end of the piston chamber so as to be subject to air compressed by the piston at one end of its stroke, said valve having a fourth pressure area; of greater extent than said additional area and the smaller of said diflerential areas when combined and for overcoming the latter, and means controlled by the piston for intermittently subjecting said fourth area of said valve to fluid pressure.

11. In a fluid pressure motor, a cylinder providinga piston chamber, a pistonreciprocable therein, a motive fluid controlling valve for said piston having two opposed pressure areas constantly exposed to live motive fluid, one of which is larger than the other, a compression; shift area opposed to the larger-of said two opposedpressure areas constantly in communication with the piston chamber, and a shift area, opposed to said compression shift area, intermittently brought into communication with said piston chamber by the reciprocations of said piston.

12. I11 a fluid pressure motor, a cylinder providing a piston chamber, a piston reciprocable therein, a fluid pressure valve, one end of which operates to control admittance of fluid pressure to one end of said piston chamber and the other end of said valve operating to control admittance of fluid pressure to the other end of said piston chamber, said valve having a compression shift areaconstantly in communication with one end of said piston chamber to shift said valve in one direction and a shift area, opposed to said compression area to which pressure fluid is intermittently admitted from said piston chamber by the reciprocations of said piston to shift said valve in the opposite direction.

13. In a fluid pressure motor, a cylinder providing a piston chamber, a piston therein, a fluid pressure controlling valve having a bore centrally therethrough, the ends of said valve cooperating with the ends of the valve chamber to control admittance of motive fluid to the ends of said piston chamber, said valve having a compression shifting area to shift said valve in one direction and a shift area opposed to said compression area and to which pressure fluid is intermittently admitted from said piston chamber by the reciprocations of said piston to shift said valve in the opposite direction.

14. In a fluid pressure motor, a fluid pressure controlling valve having a small and a large pressure area opposed by a second small and a second large pressure area, said areas being of such relative extent that said first mentioned small area is smaller than said second small area, the sum of said first small and first large areas is greater than said second small area, and the sum of said second small and large areas is greater than the sum of said first small and large areas, one of said small areas being intermittently put in communication with the piston chamber of the motor by the reciprocations of said valve.

15. In a fluid pressure motor, a fluid pressure controlling valve having a small and a large pressure area opposed by a second small and a second large pressure area, said areas being of such relative extent that said first 'inentioned small area is smialler than said second small area, the sum of said first small and first large areas is greater than said second small area, and the sum of said second small and large areas is greater than the sum of said first small and large areas, both said small areas being intermittently and alternately put in communication with the piston chamber of the motor by the reciprocations of said valve,

16. A valve for a fluid pressure tool comprising a tubular member having difl'erential end areas continuously exposed to the fluid pressure source, said member being enlarged adjacent the smaller of said differential areas to provide a shoulder presenting anadditional area for assisting said sm'aller differential area to shift the Valve, said member having an annularly projecting flange to provide a shift area opposed to and exceeding in extent the sum of said smaller differential area and of said additional area.

17. A valve for a fluid pressure tool comprising a tubular member having diflerential end areas continuously exposed to the fluid pressure source, said member being enlarged adjacent the smaller of said diflerential areas to provide a shoulder presenting an additional area for assisting said smaller differential area to shift the valve, said member having an annularly projecting flange to provide a shift area opposed to and exceeding in extent the sum of said smaller diflierential area and of said additional area, said member having a port of restricted size extending radially therethrough intermediate said smaller diflerential area and said additional area.

Signed by me at Detroit, in the county of Wayne, and State of Michigan, this 16th day of October, 1928.

GUSTAVE M. NELL. 

